Cylinder-piston type actuators of a wide range of dimensions are utilized in a multitude of applications, in most of which a machine part that has been actuated by projection of the piston, exerts a continuing load on the actuator tending to cause the piston to retract. In hydraulic actuators, this reactive load may be held by blocking return flow of the hydraulic fluid into the cylinder, as by means of an appropriate valve. The same is true of pneumatic actuators. Such actuators are usually heavy and cumbersome and are not suitable for uses wherein a small, lightweight (miniature) actuator is required, as in missiles which do not require any resetting of their actuators for subsequent use, once they have been actuated.
In the patented art, the patent to Fritz U.S. Pat. No. 3,111,808 discloses a single-stroke actuator in which a piston is driven by detonation of an explosive charge, from a retracted position to a projected position in which it is held against return movement by penetration of a sharp edge at the trailing end of the piston into the cylinder wall under the reactive load (e.g. air pressure) tending to thrust the piston back into the cylinder. An actuator or propelling device having an explosive charge-propelled piston is also disclosed in Barr U.S. Pat. No. 3,119,302. Davis U.S. Pat. No. 2,132,148 discloses a piston held within a cylinder by a split ring retainer. Other patents disclosing devices powered by explosive charges are: Gross U.S. Pat. No. 2,742,697, Stupian U.S. Pat. No. 2,897,799, Bohl U.S. Pat. No. 2,924,147 and Stott U.S. Pat. No. 2,942,818.